A Numerical Study of Summer Precipitation in the Changjiang River and the Huaihe River Valleys Within Coming Half Century
未来半个世纪江淮流域夏季降水变化趋势的数值模拟结果分析

The precipitation change in the future over the Changjiang River and the Huaihe River valleys of China in response to the global climate change has been of great concern.However the results from different research would be controversial.Different model used and different scenarios of greenhouse gas concerned would lead to different conclusions.In this study,based on the output of the GFDL R30 coupled climate model under the latest scenarios forcing of A2 and B2 released by the United Nation's Intergovernmental Panel on Climate Change(IPCC) Special Report on Emission Scenarios(SRES),the simulated current climatological state of precipitation over the Changjiang River and the Huaihe River valleys and the general circulation over East Asia and northern West Pacific are proved reasonable,and then the long-term trend of precipitation in the Changjiang River and the Huaihe River valleys within coming half century are assessed.It is revealed that after experiencing more precipitation in the first ten years of this century,there will be a long period with less precipitation in summer over this area after the year of 2010.The range of this period will be longer till the end of the 2050s of this century with a normal state period in the 2020s under the A2 scenario in which there is more greenhouse gas and SO_(2)extricated into atmosphere.Comparatively,a less precipitation period will end at the middle 2020s under the B2 scenario with less greenhouse gas and SO_(2)extricated into atmosphere.The reduced precipitation over this area results from the weaker and eastward retreating subtropical high over the northern West Pacific in summer,accompanying by weaker summer monsoon and weaker upward motion of air in the troposphere.The weakening and eastward retreating subtropical high is related to the decreasing of sea surface temperature gradient between the tropical and middle-latitude North Pacific.